Electrolytic zinc bath



Patented Feb. 3, 1931 PATENT OFFVICE GIUSEPPE BIAN CO, OI TUBIN, ITALY ELECTROLYTIC ZINC BATH Ill'o Drawing.

This invention relates to. a novel electrolytic zinc bath by means of which iron, steel I or cast iron articles can be'poated'with a perfectly uniform, smooth and compact layer of high grade zinc.

The purpose of the present invention is to provide an electrolytic bath of great stabili-' ty which shall be automatically regenerated without adding any fresh ingredients thereto i0 and is therefore. capable of working in a con-.

tinuous ma'nner and for anunlimtted period of time without necessitating any regenerating process like electrolytic baths, known heretofore.

consists in the fact that the zinccoated ar ticles are absolutely free from any spongy zones which, as is well known, occur quite often in the zinc coated articles obtained with the usual electrolytic processes and are always the soltrce of corrosions due to the natural agents. 1

A further feature of this electrolytic bath is that it allows ,to regulate at will the depth of the layendeposited and to accelerate the zinc depositio by employing high current intensities, wit out. altering 1n the least the structure of the metal and the adherence of the zinc layer.

' In known zinc baths, the electrolyte is generally made of zinc sulphate and conductive salts dissolved in water; these solutions have the drawback thatthey' are not perfectly homogeneous'and are rapidly exhausted Moreover, owing to the large quantity, of hydrogen set oflatithe cathodewith the use of those known electrolytes the production of a compact deposit free from spongy zones on large surfaces meets with serious difliculties.

This invention com letely obviates the i above mentioned draw links by employing zinc in combinatioii with mercury, sulphuric acid, phosphoric acid, conductive salts and distilled water. I

The solutiongis prepared as follows: I first make by menia zinc and mercury to an amalgam in" thg proportions hereinafter described which, byflowerin-g the meltiqi point of zinc, makes possible to deprive e zinc Application filed April 20,

mercury 1 to 15.

An important feature of this invention-- 1927. Serial No. 185,885.,

of any impurity therein contained that produces objectionable disturbances during the eleetrodeposition of the zinc. The molten amalgam thus-purified is successivel projected into a refrigerating liquid t ereby obtaining the special porous form mentioned above and containing ,both metals in the following proportions in weight, zinc 100 to 200,

The product is dissolved in distilled water to which sulphuric acid, phosphoric acid and the conductive salts have been previously added. This mass rapidly reacts develop-' ing heat and when the reaction is completed the solution, is clarified and filtered and the liquid ready for use is obtained. I also obtainthe said porous zinc 'by melting it in the presence of iron and projecting it into a refrigerating liquid as explained and in this case successively adding mercury together with the other above mentioned substances during formation of the mixture.

I The presence of phosphorus which, as is well known, has a strong affinity with nascent hydrogen, makes it possible to completely eliminate during the electrodepositionathe spongy zones on the surfaces of iron, steel or other metal coated with zinc. In fact phosphorus, added in the form of an elemenwhich prevents the formation of free hydrogen at the cathode by binding nascent hydroen. The solution that has practically given the best results .is obtained with the following substances in the proportions indicated:

7 Parts by weight Zinc-mercury amalgam 101 to 215 Sulphuric acid-" n 125 to 275 Double sulphate of iron and alumina 15 to 40 Phosphoric acid 5 to 15 Sodium and potassium hydroxide 5 to 15 Distilled waterl n 1000 The secondary constituents of the electrolyte can also be used in the form of slmple 2 memes or double compounds corresponding to the acids and bases mentioned above.

What claim is:

1. An electrolytic zinc hath comprising a 5 zinc amalgam, phosphoric acid combined Wi"h an alkali metal, sulphuric acid, aluminium hydroxide, and Water.

2. An electrolytic zinc bath containing:

Parts by weight Zinc-mercury amalgam 101 to 215 Sulphuric acid 125 to 275 Mixed sulphates of iron and alumina to 40 Phosphoric acid 5 to 10 15 Alkali metal hydroxide 5 to 15 Distilled Water 1000 3. An electrolytic zinc hath comprising a mixture of zinc amalgam, sulphuric acid, al-

kali metal hydroxide and a phosphorus containing substance that Will react in the solution to bind hydrogen at the cathode.

4. An electrolytic zinc bath comprisng a zinc amalgam, alkali metal hydroxide, phosphoric acid, sulphuric acid and Water.

5. An electrolytic zinc bath comprising a zinc amalgam, alkali metal hydroxide, aluminium hydroxide, a phosphoric acid, sulphuric acid and water.

so In testimony that l claim the foregoing as my invention, I have signed my name.

GIUSEPPE BIANGO. 

